1. Technical Field
The present invention relates to an image forming apparatus having a main body in which a rotating member such as an image carrier and a development roller is retained.
2. Related Art
As for image forming apparatus such as an electrophotographic copying machine and a printer, conventionally there has been employed a structure comprising a drum drive shaft and a drive shaft receiving part. The drum drive shaft is supported by a side plate of a main body and is driven to rotate by a chain sprocket. The drive shaft receiving part is formed in a resin flange which is fitted and fixed to an end of the image carrier drum. The drum drive shaft is fitted in the drive shaft receiving part, thereby conducting positioning of the image carrier drum. Also in this structure, a drive transmitter retained by the drum drive shaft is engaged with a drive transmitter receiving part formed in the resin flange, thereby rotating the image carrier drum (JP-A-62-65049).
There has been also employed another structure in which a drum drive gear as a spiral gear provided on a main body is meshed with a drum gear as a spiral gear fixed to one end of an image carrier drum, thereby rotating the image carrier drum (JP-A-63-4252).
However, attached to the both ends of the shaft of the image carrier drum are separate members, respectively. Accordingly, the coaxiality of the ends of the shaft is deteriorated so as to increase axis deviation and thus deteriorate the accuracy of position of the image carrier drum. Especially in case of a tandem-type color printer in which a plurality of image carrier drums are aligned, desired color can not be obtained unless respective colors are superposed on each other to an accuracy of several tens of micron meters. Accordingly, the deterioration of the coaxiality and the axis deviation constitute serious factor of decreasing the accuracy.
In case that an image carrier drum is driven by a gear, the larger the gear the larger the number of teeth thereof is, thereby improving the accuracy and reducing the irregularity in rotation, thus improving the quality. However, in case that there is a gear integrated with the image carrier drum and the gear has an outer size larger than the outer size of the process cartridge, the gear may be caught by an intermediate transferring member or the like in an image forming apparatus during the operation for replacing the process cartridge, thus making the attachment and detachment operation difficult.